Category Archives: electronics

Can You Hear a 1-dB Change?

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Decibels are commonly used in electronic communications to describe and compare signal levels. I’ve often heard that one dB is considered to be the smallest change that a typical person can detect by ear. I recently came across this website audiocheck.net that is set up to generate different audio tones and to do a blind test of how small of a change you can detect.

I started with testing for 6-dB and 3-dB changes. Easy Peasy. Then I tried the 1-dB test. I could detect the change in level fairly consistently but I did have to concentrate. Continuing on to the 0.5-dB change, I had a very high failure rate. It was very difficult to detect that small of a change. So I have to conclude that 1 dB is about the limit for a change I can hear.

How about you? Take the test on the website and let us know how you did.

There are many other audio tests to explore on that site, including the highest frequency you can hear, the minimum pitch change you can hear, etc. Check it out: www.audiocheck.net

73 Bob K0NR

Radio Shack Brands

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Recently, Retail Ecommerce Ventures (REV) announced its purchase of certain iconic RadioShack brands and related assets. Many radio amateurs and electronics hobbyists would like to see something happen in the way of a new, improved RadioShack, whether online or via brick-and-mortar stores. RadioShack is still a strong brand but it takes more than a brand to drive success in business. Count me as a bit skeptical that anything significant will happen with this move but I would be happy to be wrong about that.

A quick look at the RadioShack.com web site reveals some cross-selling on the top of the home page to Linens+Things, Pier 1, Dressbarn, Farmerscart, The Franklin Mint and Modell’s. In what marketing universe does that make sense?

RadioShack Brands

Not too long ago, I got to looking at the list of old RadioShack brand names. I thought I was a tech-savvy RadioShack dude but quickly found out they had a boatload of brand names that I never heard of. (One could argue that RadioShack completely messed up its branding strategy with so many diverse product line brands.)

Here’s what I found:

AntennaCraft (outdoor antennas and amplifiers)
Auvio (audio/video cables, LCD TV’s, headphones, premium surge protectors and speakers)
Enercell (batteries and power)
Gigaware (computer, GPS and iPod accessories, mp3 players and accessories, as well as digital cameras, digital camera accessories)
PointMobl (Wireless Phone Accessories)
Accurian (audio and video equipment and accessories)
MyMusix (MP3 players; later marketed under the Gigaware brand)
Kronus (tools)
Optimus (formerly audio and PA/DJ equipment; later used for digital camera accessories)
Presidian (audio and video equipment, telephones, flashlights,calculators, and 2-way radios)
VoiceStar (wireless phone accessories)
Archer (wiring and antennas)
Duofone (telephones & accessories)
Micronta (scientific and educational equipment)
Realistic (used broadly for radio and audio equipment)

Source: http://www.lb7.uscourts.gov/documents/14-14713.pdf

Added to the list (based on feedback from Mark/KI7N):

Science Fair electronic kits
Road Patrol bicycle electronics, radar detectors, mobile electronics
Tandy Computer personal computers

And if you want to go deeper, here is a history page on the RadioShack company.

Maybe they will bring back the Battery-A-Month Club.

73 Bob K0NR

HT and Light Bulb Load

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The light-bulb dummy load has been used with HF transceivers from way back in the old days (and sometimes more recently). These “dummy loads” tended to radiate a bit and can actually be used as a (poor) antenna. A few years ago, the Lightbulb QSO Party promoted the use of light bulbs as antennas during their event.

I wanted to find out if I could do the same thing with a 5W handheld transceiver, so I scavenged a bulb from an old string of Christmas tree lights and hooked it up to my Yaesu FT-60. This video shows what happened next.

After I made the video, I checked the specs on the FT-60 and found that the transmit power settings are: 5.0 W (High) / 2.0 W (Middle) / 0.5 W (Low). In the video, I said the middle setting was one half watt, which is incorrect.

I checked the SWR on the light bulb and found it to be 2.7. I was not worried about damaging the handheld radio because they are designed to work into crummy antennas such as the standard rubber duck.

I hope you enjoyed this fun experiment. Sorry about the amateurish video quality…I just shot it with my iPhone and did some simple editing.

73 Bob K0NR

Radio Frequency Interference From 12V-to-USB Adapters

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Many small electronic devices have switching regulators in them that can generate a bunch of Radio Frequency Interference (RFI). This is not my first encounter with RFI-spewing devices. See this article about a automotive 12V-to-USB adapter giving me trouble: This Interference Seems To Follow Me Everywhere

I recently bought a couple of adapters that are physically larger than the one I wrote about. I was thinking that a larger size might allow for a little more filtering and a design that does not radiate. I was half right: one of them works pretty well, the other is an RFI Bad Boy.

Take a look at this short video where I check them out.

 

 

 

This is an Amazon link to the adapter that works pretty well.
Enercell® 2-Port USB CLA Car Charger

 

73, Bob K0NR

ISO-TIP 7700 Soldering Iron Review

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Model 7700
Model 7700 soldering iron

I recently had the opportunity to try out a new ISO-TIP 7700 soldering iron. This is a rechargeable soldering iron without a lot of extra features but it is plenty capable for small soldering tasks. Here’s a few specs from the ISO-TIP web site:

MODEL #7700
– Fully recharges in 3.5 to 4.0 hours
– Partially charged battery to full capacity in one to two hours
– Up to 125 soldering joints per charge during continuous use
– Withstands high-rate charging without damage
I’ve been on the lookout for a simple construction project for our local radio club and had acquired a Blinkey Kit from rainbowkits.com. This is a simple two-LED flasher circuit using the venerable 555 timer. I decided it was also a great little project to try out the 7700 soldering iron. Assembly was very simple, requiring 24 solder joints. The iron did a find job of heating up those joints. It takes about 2 to 3 seconds for the tip to heat up, plenty fast for my needs.
IMG_0414soldering
Soldering iron in action

Here’s a short video of the circuit blinking away, proving that I can solder together a simple circuit: Video of circuit blinking Yes, the circuit did work the first time.

The soldering iron performed well, no complaints at all. With only 24 joints to solder, I did not stress the capacity of the iron (which is rated at 125 joints). This is a relatively light duty iron, so I wondered how well it would do against a physically large soldering task. Soldering a PL-259 coaxial connector is a common task for amateur radio work, one that takes a lot of heat. I was surprised to find that the 7700 was able to heat up the center pin of the connector quite nicely. I was not surprised that it struggled with heating the body of the connector. I think that is asking too much of this size soldering iron. The only nit I would pick is I’d really like a LED power/charging indicator. I am always nervous about whether a device is plugged in, getting power, really charging and a simple indicator would solve that. But that is a very minor issue and probably speaks more about my personal paranoia than the soldering iron.
This iron has quickly become my “Go To” tool for quick soldering jobs. I don’t do major kit assembly and other big soldering tasks. I just need a little soldering here and there and this baby is always in the charging stand ready to go. To order the soldering iron (and see other products), visit http://www.iso-tip.com/products-page/
Use discount code YT1510 to get 10% off store wide.
73, Bob K0NR
Disclosure: this soldering iron was provided to me by ISO-TIP at no charge.

Meet the Arc Fault Circuit Interrupter

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afci-receptacleYou are probably familiar with the Ground Fault Circuit Interrupter (GFCI), also called Ground Fault Interrupter (GFI), Residual-Current Device (RCD) and a few other names. While doing some electrical work for a family member, I discovered Arc Fault Circuit Interrupters (AFCIs) in the breaker box. Having a genuine Electrical Engineering degree (two, actually), I’d like to believe that I am reasonably up to date on basic house wiring. But somehow AFCIs had escaped my attention, even though they started appearing in the National Electric Code over 10 years ago.

A bit of searching on the internet revealed that these newfangled devices are intended to detect arc faults that are below the trip level of a normal circuit breaker. Think in terms of a frayed extension cord that arcs over, creating a fire hazard, but not exceeding the 15 ampere rating of a typical house circuit. As usual, the Wikipedia entry is a good place to start. AFCIs detect arcs by monitoring the current behavior throughout the 60 Hz cycle. There are characteristics in the waveform that indicate an arc condition exists, causing the AFCI to disconnect the circuit. This article goes into more technical detail if you are interested:

New Technology for Preventing Residential Electrical Fires: Arc-Fault Circuit Interrupters (AFCIs)

Just like GFIs, AFCIs are available for installation in the main breaker panel and for installation at the electrical outlet. The diagram below shows the block diagram of a typical single-phase AFCI. This is not your old school circuit breaker but a complex system that performs both arc and ground fault detection. As already mentioned, the arc detection is performed by sensing the current behavior. The ground fault detection senses the difference between the current leaving and returning to the device. If there is a significant mismatch between the two currents, a ground fault has occurred.

From New Technology for Preventing Residential Electrical Fires: Arc-Fault Circuit Interrupters (AFCIs)
From “New Technology for Preventing Residential Electrical Fires: Arc-Fault Circuit Interrupters (AFCIs)”

This post is just a quick introduction to AFCIs, with a USA perspective. Your local building codes are now or will soon be requiring AFCIs on new construction, so you’ll probably encounter them sooner or later. The National Electrical Manufacturers Association has a website with additional information: www.afcisafety.org.

73, Bob K0NR

Bloody Proprietary Connectors

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I came across this video rant by David L. Jones on the EEVblog concerning proprietary cables on consumer devices. I agree with him completely. Warning: some language not suitable for kids.

Unfortunately, if you look at ham radio gear, we are in even worse shape than the consumer market. Heck, even the freaking microphone connectors are unique to each manufacturer.

Bdale KB0G Makes Stuff!

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Last week, I had lunch with an old friend, Bdale Garbee (KB0G). Bdale and I had both worked at HP for a number of years and we have been involved in some common ham radio clubs and activities. I followed the test and measurement path with Agilent Technologies when that company was formed, while Bdale stayed with the HP computer business. He is a recognized industry expert in Unix, Linux and all things open source. It is always cool to catch up with him and find out what he has been doing. He recently took early retirement from HP…I am not sure what “retirement” means for Bdale but its not playing shuffleboard at the retirement home!

Coincidentally, a few days later, I came across this video from HamRadioNow of Bdale talking at the ARRL/TAPR Digital Communications Conference. In this talk, Bdale discusses the general theme of making stuff and the satisfaction that is derived from that activity. It is about an hour long so grab a cup of your favorite beverage and take a seat.

 

By the way, check out the other HamRadioNow videos, especially the videos of the DCC technical talks. Good stuff!

73, Bob K0NR

Easy Online Circuit Analysis

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I was writing an electronics article today and started to do some circuit analysis by hand. It was a pretty simple circuit so I knew I could crank out the circuit analysis on paper but I started to think maybe there was a better way. I poked around the web and came across CircuitLab.com, a free, online circuit simulator.

A sample circuit from the CircuitLab web site.

As I gave it a try, I was amazed at how easy it was to use. I just started doing some simple drag-and-drop from my browser and the circuit quickly took shape. A few minutes later, I had my first analysis running and I started playing “what if” games with the circuit parameters.

OK, I’ll admit that the circuit I created was pretty simple but still, I am impressed. Oh, and did I mention that its free? If you have need for circuit diagrams and simulation, check out CircuitLab.com.

– 73, Bob K0NR